Antenna



A. S. MEIER Sept. 21, 1948,

ANTENNA 3 Sheets-Shegt 1 Filed Oct. 3, 1944 F/Gl Sept; 21-, 1948. v A.s. MEIER 2,449,562

ANTENNA Filed 001:. 3, 1944 l 3 Sheets-Sheet 2 2 23 25 INVENTOR.

K7 TTOR/VEY Patented Sept. 21, 1948 ANTENNA Allen S. Meier, Xenia, Ohio,assignor to the United States of America as represented by the Secretaryof War Application October 3, 1944, Serial No. 557,038

(Granted under the act of March 3, 1883, as amended April 30, 1928; 3'700. G. 757) 2 Claims.

The invention described herein may be manufactured and used by or forthe Government for governmental purposes, without the payment to me ofany royalty thereon. v

This invention relates to antennas and more particularly to an antennaarrangement having broad band characteristics. I

Antennas that areto be mounted upon airborne craft are designed to havefavorable aerodynamic qualities. For this reason, stub. whip and loopantennas that have had good transmission characteristics, haveenjoyedwidespread acceptance and use. Antennas of these types have beencharacterized by limitations in the bandwidths of the signals that theywill transmit with optimum performance. ..In the past, the usual methodof adapting an antenna to the radiation of electrical signals of broadbandwidths was to increase .thev lateral dimensions of the antenna,since the bandwidth is a function of the ratio of the length of theantenna to its breadth. Where broad band signals are to be transmitted,antennas that have been available heretofore have been hollow sheetmetal bodies of closed cylindrical, spherical, conical, and waistedshapes that are not aerodynamically sound because of their very largeair drag, and that are too conspicuous for tactical purposes at lowfrequencies. The characteristics of these antennas are such that for thetransmission of bands of some widths that are becoming increasinglyimportant in some phases of radio work, these hollow antennas would ofnecessity be prohibitively large.

Heretofore, little attention has been paid to the physical contour ofthe surface area in the immediate vicinity of the base of an antennamounted thereon other than to specify that it should be a flat groundplane.

The objects of the present invention include the provision of antennaand fuselage associated constructions that take advantage of physicalrelations between small-diameter antennas of conventionally acceptablelengths and dimensions, and the contours of surface areas in theimmediate vicinity of the bases of antennas that are mounted thereon,that have been neglected or ignored heretofore; in antenna and mountingassemblies that have markedly improved electrical characteristics in thewidth of the signal band that the antenna will conduct or transducewithout retuning; in the provision of antenna mountings and antennacombinations wherein the antennas haverelatively small lateraldimensions and that provide tactically inconspicuous antenna assembliesthat are suitable for the transmissions of abroad band of frequencies;and in the provision of both permanently mounted and retractableimproved forms of broad band antennas that are aerodynamically sound.

With the above and other objects in view that will be apparent to thosewho are informed in the field of radio antennas, suitable illustrativeembodiments of broad band antennas and the mountings therefor thatembody the present invention are illustrated in the accompanyingdrawings, wherein:

Fig. 1 is a fragmentary side elevation of an improved antenna and acurved mounting surface assembly which embodies the present invention;

Fig. 2 is an enlarged fragmentary axial section of the assembly that isshown in Fig. 1;

Fig. 3 is a fragmentary side elevation of a modified antenna and acurved mounting surfaceassembly that is retractable toward the interiorof an aircraft or the like on which it may be mounted;

Fig. 4 is a fragmentary axial section of the assembly that is shown inFig. 3;

Fig. 5 is a diagram showing approximately the radiation pattern,projected upon a vertical plane, of a Whip antenna mounted upon a flatground plane;

Fig. 6 is a diagram showing approximately the radiation pattern,projected upon a vertical plane, of a whip antenna mounted upon a curvedplane in conformity with the present invention; and

' Fig. 7 is a graphical presentation of approximately the resistance andreactance with frequency curves of an antenna mounted upon a flat groundplane in comparison with the same antenna mounted upon a curved groundplane to embody the present invention. 1

The first form of antenna and antenna mounting assembly that is shown inFigs. 1 and 2 of the accompanying drawings, is illustrative of a usualform of antenna mounted upon a conducting surface having a sufflcientlycurved contour to impart broad band characteristics to the antenna.

The improved form of antenna assembly that is shown in these figures ofthe drawing comprises an antenna l of the whip type and of a desiredlength. The improved antenna I has a thrust assuming portion, such as aflange 2 or the like, spaced upwardly from the lower end thereof. Theantenna flange 2 rests upon the upper face of a centrally tappedoutwardly frusto-conical socket 3 that seats within a correspondinglyshaped apex].-

3 ture that is disposed centrally of a preferably circular dielectricmount 4. The mount 4 is secured to a conducting surface 5 of a desiredcurved contour, such as cylindrical, oval, round or other desired shapein any desired manner, as by bolts 6 and nuts 1, or the like. Thesurface 5 may be a special mounting for the antenna I, the skin of anaeroplane at the oval or cylindrical part thereof, or other suitablesupport. The socket 3 is firmly secured within the aperture in thedielectric mount 4 in any suitable manner, as by the use of a nut 8 thatturns upon-the threaded lower end of the socket 3. A washer l8, beneaththe nut 8, extends radially to overlie an adjacent area on the lowerface of the mount 4.

The antenna I is seated firmly within the bore of the socket 3 in anysuitable manner and prefer ably by a flanged screw 9 that turns up :intothe tapped and threaded lower end of the antenna l. A shoulder on thescrew 3 extends radially to overlie the lower end of the socket 3.Tightening the screw 9 upon the socket Bdraws the antenna flange 2tightly against the upper end of the socket 3. The screw 9 preferablycontinues downwardly to provide a central contact 13 for a connectionfitting that is accessible from within an aircraft. An outer contact His spaced from the inner contact ID with an insulating material 52interposed therebetween to complete a coaxial con nector for the antennal. Screws 13 extend thru apertures adjacent the periphery of a connectorhousing aperture that preferably is countersunk in the bottom of acylindrical hollow case It, and thread into a strengthening plate l5.The case 14 is secured to the under side of the curved mounting surface5, by the nuts I.

A modified antennaassembly that also is applied to a surface ofelectrical conducting material of a desired degree of curvature, isshown in Figs.3 and 4 of the drawings.

In this improved antenna and mounting assembly, an antenna l8 preferablyhas a frustoconical lower portion I9 that is drawn tightly into a matingaperture in a substantially cylindrical dielectriomount by suitablemeans such as by 1 a nut 2| or the like,'with or without a washer llinterposedtherebetween. A screw 22 threads into the lower end of theantenna and terminates downwardly in an axially split central contact 23for the connection of a coaxial fitting thereto. An insulating material24 is disposed between the central contact 23 and an outer contact 25part of the coaxial connector. The coaxial connector outer contact 25continues upwardly-with its upper end spot welded or otherwise securedto or continuous with a radially outwardly extending flange 26. Aplurality of screws 21 extend thru a disk 29, the flange 26 and threadinto the dielectric mount 20 to secure these parts of the assemblytogether. The open upper rim of a cylindrical hollow case 28 is securedto an axially extending flange on the disc 29 by screws 30 or the like.A strengthening collar 4| is preferably welded to the case 28 around theaperture within which the outer contact 25 is disposed.

The antenna assembly that is shown in Figs. 3 and 4 of the drawingpreferably is made to be retractable to within the inside of the planefuselage or other curved mounting in a suitable manner. The cylindricaldielectric mount 20 preferably is provided with diametrically projectingpins 3l that enter bayonet slots 32 in a hollow cylindrical sleeve 33.The sleeve 33 is secured in any suitable manner to the curved surface 5as by bolts 34 and nuts 35 that extend thru rings 36 and 3'! or thelike, one of which is welded or otherwise secured alon its radiallyinner edge to the radially outer surface of the sleeve 33.

The pins 3| are maintained yieldingly seated within the lowermost partsof the slots .32 by suitable means, such as by a wave spring 38 that isinterposed between wear rings 39 and 40 that are disposed upon the axialopposite sides of the wave spring 38 to bear against the lower edge ofthe sleeve 33 and the upper face of disc 2-3, respectively. Theresilience of the spring 38 provides a secure electrical groundconnection and also holds the assembly firmly together.

In the installation or removal of the mount 20 within the sleeve 33, theyielding resistance of the spring 38 is overcome before the pins 3| maybe seated in or removed from, the lowermost parts of the slots 32.Gaskets, not shown, serve to seal the various junctions of the parts ofthe antenna and mounts that are disclosed herein wherever needed, forminimizing the undesirable entrance of water, dust, wind and the like,into the interior of the ship or other craft upon which the antennaassemblies may be installed.

The described antennas are illustrative of aerodynamically sound, smalldiameter antennas that have been adapted for broad band work by havingthe present invention embodied thereinto. It has been determinedexperimentally that an antenna of small diameter and of commonlyavailable or of conventional design that is built in combination with acurved surface in such -a manner as to embody the present invention isthereby adapted for the conducting of electrical impulses of band widthsthat Were outside of the range of the same antennas on their usual flatground plane mounting. A whip antenna that embodies the presentinvention has an improved radiation pattern and its bandwidth ismaterially greater than the bandwidth that is obtained from the sameantenna when used on a flat ground plane, the bandwidths being comparedat the same radiation resistance level, such as the fifty ohm level, forexample.

"Comparable radiation patterns projected ona flat vertical plane of awhip antenna are shown in Figs. 5 and 6 of the accompanying drawings.The pattern that is shown in Fig. 5 is that of a whip antenna mountedupon a fiat ground plane. The pattern provides good contact withneighboring planes both laterally and above the point at which theantenna is fed but provides little or no contact with neighboring planeslaterally and below the point at which the antennais fed.

The pattern that is shown in Fig. 6 is that of the same whip antennamounted upon a curved ground plane to embody the present invention. Thepattern providesgood contact-with neighborin planes laterally and bothabove and below the point of contact at which :the antenna 'is fed.

It will thus be-seen that the present invention materially enlarges theantenna radiation pattern to include the lateral zone below an aeroplanethat is provided therewith, which 'heretofore has been a common blindspot in interplane communications.

The curves that are shown'in Fig. 7 of the accompanying drawingsillustrate the approximate increases in band width at a given resistancelevel of an antenna mounted upon a curved ground surface to embody thepresent invention, as compared with the same antenna mounted upon a flatground plane. The resistance-frequency curve is shown to the left ofFig. 7 and the reactance-frequency curve is shown to the right of Fig.7. It has been determined experimentally that an antenna that is mountedupon a curved surface to embody the present invention has a materiallybroader bandwidth at the same level than the same antenna mounted upon aflat ground plane.

This result finds its explanation in viewing the present invention as acenter-fed di-pole an tenna. Viewed in this manner the antenna 1provides one pole of the di-pole and the curved conducting surface 5,that joins the antenna 1 at its base and at the feeding point for bothpoles, provides the other and laterally expanded pole for the di-poleantenna. With this view of the present invention in mind the matter ofaccounting for the functional advantages of the present invention willbe more apparent.

In conformity with the accepted theory of Marconi antennas the currentis zero at the extreme end of the antenna and is at a maximum at thepoint at which power is fed into the antenna. An antenna assembly thatembodies the present invention is not used alone but is used with anexpanded counterpoise in the form of the curved antenna supportingconducting surface 5.

With the maximum current fed into the antenna system at the junction ofthe antenna l and its counterpoise or expanded image 5. it is logical toassume that the electrical fields that are roughly axial to the antenna1 continue in a laterally expanded form about the counterpoise 5. By thesame reasoning, it is logical to assume that the magnetic fields thatare normal to the electrical fields thruout are similarly expanded aboutthe counterpoise 5. The deduction properly follows that the type andcharacteristics of the signals that emanate from an antenna assemblythat embodies the present invention have a. form that differs from thosethat emanate from an antenna I on its usual fiat mounting surface. Thistheoretical deduction has been substantiated in fact in thatconventionally accessible antennas when mounted in conformity with thepresent invention have been found to have a materially increasedbandwidth in performance, as compared with the same antennas onconventional mountings.

It is to be understood that the type of antenna and the mountingtherefor that have been disclosed and illustrated herein have beensubmitted for the purposes of illustrating and explaining the presentinvention and that other forms of slender antennas and curved mountingstherefor may be substituted for the particu lar constructions that havebeen chosen for this explanation without departing from the presentinvention as defined by the appended claims.

What I claim is:

1. An antenna and mounting assembly, comprising in combination anantenna having a radially projecting flange spaced from the input endthereof, a socket into the bore of which said antenna is removablydisposed with the antenna flange engaging one end thereof and having afrusto-conical outer surface, a dielectric mount that is apertured toreceive and provide a mating seat for said socket, means for drawingsaid socket securely into the aperture in said mount, means engagingsaid socket for drawing the antenna flange tightly against the end ofsaid socket that is contacted thereby and which means continues toprovide an antenna contact, electrical conducting means upon which saidmount is secured, and a case in electrical connection with theelectrical connecting means and continuing to provide a contacttherefor.

2. An antenna and mounting therefor, comprising in combination anantenna having a tapered lower end, a dielectric mount apertured toreceive and substantially mate with the tapered lower end of saidantenna, means for drawing the tapered end of said antenna snugly intothe mating aperture in said mount, an antenna contact electricallyconnected to said antenna, a pair of pins extending laterally from saidmount, a sleeve for receiving said antenna mount and slotted to receiveand releasably secure the pins from said mount, spring means yieldinglysecuring the mount pins in the sleeve slots, and a ground contactinsulated from said antenna contact.

ALLEN S. MEIER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,305,104 Hewitt May 27, 19192,170,849 Berndt Aug. 29, 1939 2,184,729 Bailey Dec. 26, 1939 2,235,139Bruce Mar. 18, 1941 2,239,724 Lindenblad Apr. 29, 1941 2,258,953 HigginsOct. 14, 1941 2,266,139 Zukerman Dec. 16, 1941 2,267,951 RoosensteinDec. 30, 1941 2,313,046 Bruce Mar. 9, 1943 2,354,314 Harsted July 25,1944 2,368,663 Kandoian Feb. 6, 1945 2,404,093 Van B. Roberts July 16,1946 FOREIGN PATENTS Number Country Date 813,957 France Mar. 8, 1937OTHER REFERENCES Biconical Electromagnetic Horns, Proceedings of theIRE, December 1939, pp. 769-700.

